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Thread: 56 Roadmaster Trany/Rearend Swap

  1. #1

    56 Roadmaster Trany/Rearend Swap

    My Dynaflow decided to call it quits. It can barely pull the Roadmaster out of the garage and when it does it leaves "pints" of transmission fluid behind -- yep I said pints -- and yes - the drain pan is still there.

    Anyway, I'm considering upgrading to a 700R4. Bendtsen's (http://www.transmissionadapters.com/index.htm) has a kit and can provide me a rebuilt 700R4. I have to replace the drivetrain and the rearend as well.

    Has anyone else performed this upgrade on a 56? If so, what rearend did you change to?

    Thanks
    BJ

  2. #2
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    trans swap

    one of our contributors to this forum has his own site. look up 'Jyrki,s buick site' in google and he has some nice pics of his installation on a 48 buick chassis. The Buick chassis are all similar in design up to 1956, so this will give you an idea of whats neccessary to adapt an available more up to date open drive rear end assembly.

  3. #3
    that site was awesome. some cool stuff and ideas for me. i wanna make a custome intake manifold now.

  4. #4
    In '56 Buick "kinda" changed the design of the differential. '55 & back had c-clips & '56 up had press-on axle bearings. They still used the 9 3/8ths. ring & pinion set-up, which started in the 30's sometime & carried on till '76 in the big cars. This rear was also used on some of the bigger Olds & Pontiacsin the late 60's to '76. If you or anyone has the opportunity to do so, put a '56-'58 up on a lift & along side on another lift put a full size '61-'70 on the lift, expecially '63-'70 Rivs. & others that still use the X-Frame from '61-'65. You would be amazed at how close everything is. You would measure & remove all brackets from the donor to install on the '56. Factory engineered with 12" brakes just like stock. The downside is that these rears are very strong so seldom do they break or require repairs. This sometimes makes it difficult to find bearings or some other parts, but they are available. Performance wise there is no aftermarket for hi-performance ring & pinion sets, so if you want performance you will look long & hard for the more desireable ratios like 3.42/3.64/3.90, which you would use behind a 700R4. Very common are 3.07/3.23 & some others in the 2 series. These are good for cruisin' the highways & by-ways. If you use an O/Drive trans. behind any of these cruiser gear ratios the ole 322 will be lugging big time unless you like cruisin' at 80-100MPH. Get an adapter from Bob to use a TH350 or TH400 with the cruiser gears & you'll be a happy camper.
    Just my nickels worth.

    Tom Telesco

  5. #5
    Tom,
    "unless you like cruisin' at 80-100MPH"
    As it turns out that is a nice speed to cruise at, unfortunately my wife (and the State of Minnesota Highway Patrol) strongly discourage such activity so I guess I'll have to settle for something less.

    Thanks for the advice. I've got some more research to do. I believe the folks I know who suggested the 700R4 did so because of its durability reputation (and the fact that they have more HP under the hood than my 322).

    BJ

  6. #6
    Bob, for all intent purposes the 700R4 is an O/D turbo 350. It may not be as durable as one thinks but can be built to take some abuse if built properly. Everyone seems to favor the 200/4R, not because of durability but more for the availability of being easier to upgrade, it also takes less HP to operate. Then you also have the choice of a 4L80. Basically a TH400 with O/D. These are more or less bullet proof. Somewhat like our ole NailHeads.

    Tom T.

  7. #7
    Thanks again Tom..

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